Preliminary Results from the Viking Orbiter Imaging Experiment

Abstract

During its first 30 orbits around Mars, the Viking orbiter took approximately 1000 photographic frames of the surface of Mars with resolutions that ranged from 100 meters to a little more than 1 kilometer. Most were of potential landing sites in Chryse Planitia and Cydonia and near Capri Chasma. Contiguous high-resolution coverage in these areas has led to an increased understanding of surface processes, particularly cratering, fluvial, and mass-wasting phenomena. Most of the surfaces examined appear relatively old, channel features abound, and a variety of features suggestive of permafrost have been identified. The ejecta patterns around large craters imply that fluid flow of ejecta occurred after ballistic deposition. Variable features in the photographed area appear to have changed little since observed 5 years ago from Mariner 9. A variety of atmospheric phenomena were observed, including diffuse morning hazes, both stationary and moving discrete white clouds, and wave clouds covering extensive areas.

A volcanic origin for the outflow channels of Mars: Key evidence and major implications

“…These 'outflow channels' generally head abruptly at disturbed terrain, ridged plains, or structural features and extend downslope for distances of up to several thousand kilometers (McCauley et al, 1972;Masurksy, 1973;Milton, 1973;Carr, 1974;Carr et al, 1976;Masursky et al, 1977;Mars Channel Working Group, 1983) (Fig. 1).…”

“…1). Typical attributes of outflow channels include low sinuosity, high width-to-depth ratios, the presence of streamlined erosional residuals and complex anastamosing reaches, and the presence of longitudinal grooves or ridges on exposed channel floors (e.g., Milton, 1973;Carr, 1974;Carr et al, 1976;Masursky et al, 1977;Baker, 1982;Mars Channel Working Group, 1983;Carr, 1996). The largest Martian outflow channels head in the southern highlands and extend across the topographic dichotomy boundary to the plains of the northern lowlands (e.g., Masursky et al, 1977).…”

Evidence of volcanic and glacial activity in Chryse and Acidalia Planitiae, Mars

“…The uniqueness of the northern lowlands of Mars has been evident ever since they were first imaged by Mariner 9 and Viking (Masursky, 1973;Carr et al, 1976). Those data revealed a complex and intriguing landscape populated by giant polygon-forming troughs (Mutch et al, 1976), bright-colored mounds (Allen, 1979(Allen, , 1980Frey et al, 1979), and flat-topped mountains Hodges and Moore, 1978).…”

Modes of sediment transport in channelized water flows with ramifications to the erosion of the Martian outflow channels

“…The ranges of sediment grain sizes that are transported, respectively, in these three modes are governed by the stream-flow velocity and by the settling velocities of the grains. The criteria that are commonly used to distinguish these transport modes will be summarized, and then applied to presumed channelized water flows on Mars, the flows that may have 317 eroded the large outflow channels (Milton, 1973: Sharp andMalin, 1975;Carr et al, 1976;Masursky et al, 1977). Because the reduced gravity on Mars affects both the flow velocity and the settling velocities of the transported grains, it can be expected that the proportions of bed load, suspended load and wash load would have differed in such water flows from that in terrestrial rivers.…”